Fluid-tight screw connections are necessary in manifold applications to prevent the escape of liquids or gases from a closed system. While flat seals or metallic sealing threads are partially used for this purpose, the use of thread seals is also frequently preferred in practice. The thread seals typically comprise hemp or Teflon and are wound around an external thread of the screw connection before the screwing together. The hemp fibers or the Teflon, which is used in the form of thin strips, reach the intermediate space between the external thread and the internal thread of the screw connection if correctly used and seal off this intermediate space in relation to a passage of gases or liquids.
The application of hemp or Teflon strips for sealing purposes is connected to a high time expenditure. In addition, even with extreme care, later leaks may not be precluded. Therefore, a connection element has been suggested in the prior art, whose external thread is coated using a polyamide layer. Thermoplastic sealants of this type, such as polyamide, have an array of disadvantages. One essential disadvantage is that the known sealants do not have permanent elasticity. The known sealants thus become brittle over time, so that they gradually lose their sealant properties. High temperatures or even large variations of the temperature, by which the sealant is alternately heated and cooled again, also favor the embrittlement of the sealant and thus the occurrence of leaks.
A further disadvantage affecting thermoplastic sealants in particular is that they are only usable up to a temperature of approximately 70° C. to 100° C. This temperature range is approximately coincident with the maximum permissible operating temperature of the most common line types in use. While the maximum operating temperatures of natural gas lines are at 70° C., the same temperatures are 95° C. for drinking water lines and 110° C. for heating pipes. Certainties for the functional capability of thermoplastic sealants therefore typically cannot be assumed for these and comparable applications.
A further disadvantage is the low mechanical carrying capacity of the sealants. Particularly lacquers or resins are easily damaged during transport or by incorrect handling. This also frequently results in leaks.
Moreover, the use of polyamide or epoxide resin as a sealant is limited to very specific applications.